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Merge pull request #382 from redis-performance/pr/four-digit-followup

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Add a 4-digit SWAR follow-up to loop_parse_if_eight_digits (clang)
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Daniel Lemire 2026-06-01 15:45:15 -04:00 committed by GitHub
commit ed861322d8
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include/fast_float/ascii_number.h
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@ -266,6 +266,21 @@ loop_parse_if_eight_digits(char const *&p, char const *const pend,
p)); // in rare cases, this will overflow, but that's ok
p += 8;
}
// Consume a remaining 4-7 digit run in a single SWAR step instead of
// byte-by-byte (reuses the existing 4-digit helpers). The parsed result is
// identical either way. Gated to clang: on gcc the extra 4-digit check
// regresses inputs whose remainder is shorter than 4 digits (it becomes pure
// overhead there); clang does not show that.
#if defined(__clang__)
if ((pend - p) >= 4) {
uint32_t const val4 = read4_to_u32(p);
if (is_made_of_four_digits_fast(val4)) {
i = i * 10000 +
parse_four_digits_unrolled(val4); // may overflow, that's ok
p += 4;
}
}
#endif
}
enum class parse_error {